1. Field of the Invention
The present invention relates to a magnetic angle detector capable of detecting a rotational angle of an object to be detected based on a change of magnetic flux density.
2. Description of the Related Art
A magnetic angle detector has been conventionally used to measure an angle of an output shaft of a motor. For example, Japanese Laid-open Patent Publication No. 08-122011 discloses a detector that includes detection elements arranged on a peripheral surface of a ring magnetic body.
FIG. 11A illustrates the magnetic angle detector and output thereof at a given time. As illustrated in FIG. 11A, the magnetic angle detector 100 includes a gear-shaped detected object 200, which is rotatably disposed around a rotational axis O (not illustrated). A plurality of concave and convex parts are formed at a predetermined pitch on a peripheral surface of the detected object 200. A detection body 300 that includes a magnet 390 and a magnetic detection unit 340 inside is disposed to face the peripheral surface of the detected object 200.
As illustrated in FIG. 11A, the magnetic detection unit 340 includes two magnetic detection elements 310 and 320. The two magnetic detection elements 310 and 320 are positioned between the magnet 390 and the detected object 200. A voltage Vcc is applied to the two magnetic detection elements 310 and 320.
FIG. 11B, which is similar to FIG. 11A, illustrates a state after passage of a predetermined time from that illustrated in FIG. 11A. FIG. 11C, which is similar to FIG. 11A, illustrates a state after passage of a predetermined time from that illustrated in FIG. 11B. As can be understood from FIGS. 11A to 11C, because of the plurality of concave and convex parts formed on the peripheral surface of the detected object 200, when the detected object 200 rotates around the rotational axis O (not illustrated), magnetic flux density between the magnet 390 and the detected object 200 changes. The magnetic detection elements 310 and 320 output such a change of the magnetic flux density as an output signal. Accordingly, the magnetic angle detector 100 can detect a rotational angle position of the detected object 200.
The magnetic detection elements 310 and 320 of the magnetic detection unit 340 are configured to match a plurality of concave and convex parts at a specific pitch of the detected object 200. In other words, the magnetic detection unit 340 may not be used for other detected objects including a plurality of concave and convex parts different in size of pitches.
Thus, when use of another detected object is requested, another detection body that includes magnetic detection elements matching a pitch of the other detected object must be prepared. In other words, according to the pitch type of the plurality of concave and convex parts of the detected object, a detection body matching the pitch must be manufactured and prepared. As a result, the number of manufacturing steps increases, and component management becomes complex.
The present invention has been developed in view of the aforementioned problems, and it is the object of the present invention to provide a magnetic angle detector that includes a detection body usable even when pitches of concave and convex parts of a detected object are different.